Latching mechanism for circuit breakers



Oct. 19, 1965 H. FORWALD 3,213,334

LATCHING MECHANISM FOR CIRCUIT BREAKERS Filed Dec. 2, 1963 IIIII 4 f A if a a Z6 2/ 2.2 a'; & 4 25 v1)? m s INVENTOR United States Patent 3,213,334 LATCHING MECHANISM FOR CIRCUIT BREAKERS Haakon Forwald, Ludvika, Sweden, assignor to Allmanna Svenska Elektrislra Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Dec. 2, 1963, Ser. No. 327,179 Claims priority, application Sweden, Dec. 1, 1962, 12,944/62 Claims. (Cl. 317187) This invention relates to a latching mechanism, and more specifically relates to a novel latching mechanism for gas circuit breakers wherein a portion of the latch mechanism includes a magnet structure and an armature therefor.

Latching mechanisms of various types are well known to those skilled in the art, and have wide application such as normally latching a member against motion until the occurrence of a predetermined condition. Typical latching mechanisms include mechanical blocking mechanisms which may be mechanically or magnetically released and engaged. Such blOCking mechanisms are subject to difliculty of calibration and are subject to change in calibration due to wear.

In accordance with the present invention, the complete latch structure is formed of a magnetically restrained armature member independent of any mechanical blocking action. The latch engaged position is then defeated by physically prying the armature away from the magnetic member whereby, after some critical gap distance is reached between the armature and the surface of the magnetic member, other biasing means connected to the armature can complete the unlatching operation.

Accordingly, a primary object of this invention is to provide a novel latch structure for air circuit breakers.

Another object of this invention is to provide a novel latch structure which has a constant calibration and is not subject to wear.

A further object of this invention is to provide a novel latch structure which is easily adjusted.

Yet another object of this invention is to provide a novel latch system for a complete latch arrangement which is independent of any blocking members, and is operated by prying the armature away from a co-operating magnet member.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE 1 schematically illustrates a circuit breaker in partial cross-sectional view and illustrates the use of the novel magnetic latch structure of the invention.

FIGURE 2 shows an enlarged cross-sectional view of an alternative latch structure which could be used in the arrangement of FIGURE 1.

FIGURE 3 illustrates the force characteristics of a latch constructed in accordance with the invention as a function of air gap between the armature and the magnetic member.

Referring now to FIGURE 1, I have schematically illustrated therein a compressed air circuit breaker of a well-known type which has a metallic container 1 which is permanently filled with compressed air from a suitable source (not shown). The container 1 is carried with respect to ground by a suitable insulator column 2 where the container may be at a high potential. The container 1 then carries a stationary contact 3 and a co-operable movable contact 4 which is moved into and out of engagement with contact 3. Stationary contact 3 can, for example, be carried at the end of a bushing insulator 5 which extends into container 1, as shown. Movable contact 4 is then carried in a suitable housing 6 which is also arranged in the wall of the container 1 with the movable contact permanently electrically connected to container 1.

The mechanism housing 6 is then provided with suitable outlet openings (not shown) through which air may flow from within the housing 1 when contacts 3 and 4 are opened, the air or other suitable gas blowing through the are formed between the contacts in the usual manner.

For purposes of the present invention, it is suflicient to understand that the mechanism 6 will open contact 4 and hold it in the open position so long as conduit 7 leading to mechanism 6 is filled with compressed air, while the contacts 3 and 4 are closed, and are held closed so long as conduit 7 is emptied of compressed air.

The operating mechanism for the circuit breaker will, therefore, include a suitable mechanism 8 which controls the application of compressed air to conduit 7. As will be shown more fully hereinafter, this operating mechanism will be operated by means of the axial movement of control insulators 9 and 10 which have their lower operating ends at ground potential.

The latching mechanism for the operating mechanism 8 is specifically formed by the U-shaped permanent magnets 11 and 12 which receive magnet armatures 13 and 14 respectively. Note that magnets 11 and 12 could be U-shaped magnets or could be cylindrical members, as will be described more fully with reference to FIG- URE 2.

The magnets 11 and 12 are located below cylinders 15 and 16 which receive pistons 17 and 18 respectively. Pistons 17 and 18 then have biasing springs 19 and 20 respectively located beneath pistons 17 and 18 respectively for biasing these pistons upwardly, this upward motion being normally prevented by the magnetic attraction between magnets 11 and 12 and armatures 13 and 14 respectively which are connected to pistons 17 and 18 by piston rods 21 and 22 respectively.

A pair of piston rods 23 and 24 are then coaxially arranged with respect to rods 21 and 22 respectively, as shown. Piston rod 23 is connected at its bottom to piston 25, while the top of piston rod 23 is connected to the two-way valve 26 which is biased downwardly by spring 27 which seats on top of piston 25. The two-way valve 26 is then movable from a position which normally blocks communication between conduit 28 and conduit 7 where the conduit 28 is held at the high pressure of the compressed air within housing 1. When the valve 26 is moved upwardly, conduit 28 is directly connected to the left-hand end of conduit 7.

The piston rod 24 is connected to the two-way valve 30 and is normally biased downwardly by means of the biasing spring 31. The two-way valve 30, when moved to its upward position, seals the conduit 7 from either conduit 32 or the open air, while when two-way valve 30 is in the position shown, it connects conduit 32 directly to conduit 7. The conduit 32 opens into cylinder 15 immediately above piston 17 when the piston 17 is in its upper position.

The insulators 9 and 10 are then provided at their tops with pins 33 and 34 respectively which pass through openings in the bottoms of magnets 11 and 12 resepctively, whereby rods 33 and 34 can pry armatures 13 and 14 respectively out of engagement with their respective magnets 11 and 12.

In operation, and in order to open the circuit breaker contacts 3 and 4, the insulator 9 is driven upwardly by a suitable operating mechanism (not shown). The pin 33 will, therefore, strike armature 13 and pry armature 13 out of engagement with magnet 11.

During this operation, an air gap will be created between armature 13 and magnet 11 which is large enough so that the attractive force exerted on armature 13 by magnet 11 is exceeded by the upward biasing force of spring 19. Accordingly, rod 21 moves upwardly and moves rod 23 upwardly against the force of its biasing spring 27. The position of the two-way valve 26 then changes from the position shown to a position in which conduit 28 is connected to conduit 7. The application of air to the conduit 7, as previously indicated, will cause the opening movement of movable contact 4.

It will be seen that at the same time conduit 7 fills with compressed air, the conduit 32 will also fill with compressed air through the open valve 30. Accordingly, the piston 17 will be driven downwardly until the magnet armature 13 seats upon magnet 11 and is relatched. Thus, the operating mechanism is reset and the contacts are held in their open position.

In order to close the circuit breaker, the insulator is driven upwardly by a suitable operating mechanism (not shown). This will cause member 34 to pry armature 14 away from the magnet 12, thereby ultimately causing valve 30 to move upwardly so that conduit 32 is connected to open air. The space in cylinder 15 between pistons 17 and is thereby emptied of compressed air, and the two-way valve 26 is returned to its lower position by the spring 27 The compressed air in conduit 7 can then flow out through valve 26 and conduit 29 into the cylinder 16 which carries piston 18. The piston 18 is thereby returned to the lower position shown in the drawing, whereby the opening 35 is cylinder 16 is opened and compressed air above piston 18 can flow into open air. Thus, the conduit 7 is emptied for compressed air and the movable contact moves to the closed position shown in FIGURE 1 with respect to contact 3.

It is to be noted that the ends of rods 9 and 10 are provided with fork-like extensions 36 and 37 respectively. These fork-like extensions serve as gripping means for gripping over the tops of armatures 13 and 14 respectively to pull the magnet armatures to their returned and latched position in the event that some malfunction occurs in the automatic return mechanism.

FIGURE 2 illustrates another manner in which the latching magnets of FIGURE 1 can be formed.

Referring now to FIGURE 2, the magnet structure is formed of a first cylindrical portion 40 which concentrically receives a second outer cylindrical structure 40a to define an annular air gap 4% between opposing north and south pole faces of sections 40 and 40a. The armature is then formed of a magnetic member such as armature 41. The armature 41 will then have an operating rod such as rod 44 extending therefrom which is equivalent to rods 21 and 22 in FIGURE 1. The operating mechanism for releasing the latch of FIGURE 2 is then formed by a suitable lifting rod such as rod 43 which is equivalent to rods 33 or 34 of FIGURE 1.

The force diagram of a magnet such as that shown in FIGURE 2 is illustrated in FIGURE 3 wherein the vertical axis illustrates holding force in percent, while the horizotal axis illustrates air gap separation between armature and magnet surface.

The holding force decreases as illustrated by curve a as the air gap increases. Where the magnet operates against the biasing force, for example, of a spring, the spring force can be shown as an almost constant force for very small extensions thereof, as illustrated by curve I). As seen in the diagram of FIGURE 3, the spring force is approximately equal to 60% of the holding force of the magnet. Thus, the point of intersection between curves a and b shows the air gap size when spring force begins to overcome the magnetic holding forces. The cross t hatched area to the left of this intersection point represents the energy E which, therefore, must be used to disengage the armature. In a similar manner, the cross-hatched area to the right of the intersection point represents the energy E which is produced by the spring when the spring is released.

For a typical example, it can be assumed that the holding force at the beginning of movement is equal to kg, While the spring force is equal to 60 kg. This spring force, after a movement of 1 centimeter, of the armature will decrease to 40 kg. Thus, the energy B, will be approximately 0.07 kg.-cm., While the energy E is approximately 50 kg.-cm.

This illustrates that the released energy E can be approximately 700 times as great as the releasing energy E. This large ratio of E to E cannot be obtained with previously used mechanical latches without the additional provision of rollers, links, and the like. Clearly, however, this ratio is easily obtained with a simple direct latch arrangement between a magnet and a cooperating armature structure.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred therefore that the scope of the invention be limited not by the specific disclosure herein but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. A latch mechanism comprising a magnetic holding member including a magnet part and an armature part, means mounting said parts for movement of one of the parts relative to the other part between a first position in which said parts are in contact and a second position in which said parts are separated, biasing means carried by said mechanism operatively engaging the movable one of said parts tending to produce movement between the parts to said second position, a rod, and means carried by said mechanism mounting said rod for movement into and out of engagement with the movable one of said parts, said rod upon engagement with the movable one of said parts moving such part to produce movement of the parts to such second position, said biasing means exerting a force less than the magnetic attraction between the parts when they are in said first position but greater than the magnetic attraction between the parts when they are in said second position.

2. A latch mechanism as claimed in claim 1, in which the latch mechanism includes a housing and the magnet is a permanent magnet attached to said housing.

3. An operating device according to claim 2, in which the ratio of energy in said biasing means to energy required to separate said parts to said second position is of the order of 700 to 1.

4. An operating device according to claim 3, in which said magnet part has an opening therein and said rod passes through said opening.

5. An operating device according to claim 4, in which said rod has a bifurcated portion connected therewith engageable with portions of said armature part, whereby the rod can move said armature part into engagement with magnet part.

References Cited by the Examiner UNITED STATES PATENTS 2,467,720 4/49 Austin 317-17l X 3,042,771 7/62 Oliveau. 3,084,312 4/63 Lee 317158 BERNARD A. GILHEANY, Primary Examiner. 

1. A LATCH MECHANISM COMPRISING A MAGNETIC HOLDING MEMBER INCLUDING A MAGNET PART AND AN ARMATURE PART MEANS MOUNTING SAID PARTS FOR MOVEMENT OF ONE OF THE PARTS RELATIVE TO THE OTHER PART BETWEEN A FIRST POSITION IN WHICH SAID PARTS ARE IN CONTACT AND A SECOND POSITION IN WHICH SAID PARTS ARE SEPARATED, BIASING MEANS CARRIED BY SAID MECHANISM OPERATIVELY ENGAGING THE MOVABLE ONE OF SAID PARTS TENDING TO PRODUCE MOVEMENT BETWEEN THE PARTS TO SAID SECOND POSITION, A ROD, AND MEANS CARRIED BY SAID MECHANISM MOUNTING SAID ROD FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH THE MOVABLE ONE OF SAID PARTS, SAID ROD UPON ENGAGEMENT WITH THE MOVABLE ONE OF SAID PARTS MOVING SUCH PART TO PRODUCE MOVEMENT OF THE PARTS TO SUCH SECOND POSITION, SAID BIASING MEANS EXERTING A FORCE LESS THAN THE MAGNETIC ATTRACTION BETWEEN THE PARTS WHEN THEY ARE IN SAID FIRST POSITION BUT GREATER THAN THE MAGNETIC ATTRACTION BETWEEN THE PARTS WHEN THEY ARE IN SAID SECOND POSITION. 